WO2006100984A1

WO2006100984A1 - Volume data rendering system and volume data rendering processing method

Info

Publication number: WO2006100984A1
Application number: PCT/JP2006/305148
Authority: WO
Inventors: Masataka Imura; Kunihiro Chihara; Ichiro Nakahori
Original assignee: National University Corporation NARA Institute of Science and Technology
Priority date: 2005-03-18
Filing date: 2006-03-15
Publication date: 2006-09-28
Also published as: JP4656633B2; JP2006260408A

Abstract

Volume data is inputted by a volume data acquisition module so as to create a voxel data set to which a luminance value and an opacity are given by the voxel data set creation module. When sampling a voxel from the voxel data set, a voxel is selected while allowing fluctuation according to a fluctuation model of a fluctuation processing module. An integration module calculates image data to be displayed according to the luminance value and the opacity of the sampled voxel. The display module displays the pixel data passed from a ray casting module. Furthermore, a velocity field processing module having a velocity field model performs a fluctuation processing incorporating velocity expression, so that a volume data velocity is expressed to a viewer. This provides a volume data rendering system capable of adding 3-dimensional volume data fluctuation expression and enabling a user to grasp the expression intuitionally.

Description

Specification

Volume data rendering system and volume data rendering processing method

Technical field

The present invention relates to a volume data rendering system that visualizes volume data defined in a three-dimensional space, and a volume data rendering processing method. Background art

[0002] Various expression formats for 3D computer graphics have been proposed.

In general, 3D object data is often given in plane units as a combination of polygon data and texture data. If polygon data is used, the outer surface shape of the 3D object can be defined by a mesh-like wire frame. When drawing (rendering), polygon data is arranged while adjusting the position and angle of the 3D object according to the display scene, and the drawing is done by pasting the texture data on the surface. It can be said that the representation by polygon data is an excellent representation format for 3D objects.

[0003] However, polygon data is suitable as an expression format for objects and physical phenomena represented by the density and density of particles distributed in a three-dimensional space! For example, “clouds”, which are the concentration distribution of water vapor in the atmosphere, are difficult to represent as polygon data. Depending on the concentration distribution of water vapor, the clouds absorb and scatter sunlight, and are expressed as white or gray shading, but complex and light uneven patterns continuously spread in the space. It is difficult to express with polygon data defined by mesh-like wire frames. Similarly, it is difficult to express “smoke” as polygon data.

[0004] Therefore, an expression format using volume data has been studied as a data expression format suitable for expressing the density and density of particles distributed in a three-dimensional space. Volume data is 3D array data in which the density and density of particles distributed in 3D space,! / と features, and opacity are assigned to each voxel. Here, the “botacel” is a lattice-like small cube obtained by subdividing a three-dimensional space. Fill the 3D space with botasels, and add feature values to each botasel By giving it, it is possible to appropriately define the feature quantity such as density and density of particles distributed in a three-dimensional space. Here, various feature quantities are assumed and may be given as high-dimensional data. In the above-mentioned cloud example, brightness and hue are assumed as feature quantities.

[0005] On the other hand, opacity has been introduced to give the effect of “blur” and “watermark” to 3D objects. By introducing opacity into each botasel, it is possible to give a 3D object a translucent expression, a foggy! /, And a so-called “blurring” effect.

[0006] By introducing volume data as described above, it is possible to appropriately define a three-dimensional object such as a cloud or smoke distributed in a three-dimensional space.

[0007] Next, a rendering process of a three-dimensional object defined using volume data will be described.

FIG. 10 is a diagram showing a basic flow of a rendering process procedure when volume data is used.

First, volume data is acquired (Sl). The volume data may be prepared in advance, or it may be created in real time by observing a 3D object. It is preferable to perform preprocessing such as noise removal and image enhancement necessary based on the acquired volume data.

[0009] After performing this pre-processing, the luminance value and opacity are determined for each votacel (S2) to form a voxel data set volume.

Next, a final luminance value for each pixel is obtained by ray casting processing. The ray casting process includes a sampling process (S3) and an integral calculation process (S4) based on the brightness value and opacity of the sampled botasel!

FIG. 11 is a diagram schematically illustrating the concept of ray casting processing.

Raycasting gives a line of sight 1202 in each direction from the viewpoint, and samples the botasels 1201 distributed in the volume of the botasel dataset 1200 in the three-dimensional space along the rays 1202 and samples them. This is a method of adding the feature values (luminance values) of each of the botacells 1201. If each botel is given opacity, By casting, the inside is visualized with a translucent display. In ray casting, the product of the brightness value and opacity of each botasel is added in order, and the total opacity is calculated.

When the force ray that becomes 1 penetrates the 3D object, the processing for that pixel is terminated, and the addition result is displayed as the pixel value 1301 of the drawing surface 1300.

[0011] If the luminance value and opacity at the current sample position are i and α, respectively, the pixel luminance value I by ray casting is I, and the luminance value at the time of line-of-sight input is I. It is represented by the number 1.

[0012] [Equation 1]

I ou t = I i n (1 — L) + I

[0013] The pixel value 1301 to be finally drawn is obtained by integrating all the sampled voxels in the above equation 1.

In the prior art, volume data rendering processing is performed according to the above procedure, and drawing processing (S5) is performed for each pixel on the monitor. However, the following problems have been pointed out.

The first is the high calculation cost. Volume data is calculated on the basis of each voxel spreading in a three-dimensional space, so complicated and enormous calculation is required.

Second, memory consumption is high. Since it is necessary to handle the brightness value and opacity of each botacell spread throughout the 3D space as data, a large amount of memory is consumed.

[0015] In order to solve these two problems and perform volume data rendering at high speed, it is necessary to develop a dedicated processor equipped with a special resource such as a dedicated accelerator and a large amount of memory. It had been.

[0016] In particular, when rendering volume data with a movement like smoke that does not display a stationary object such as a cloud in a stationary state in a virtual reality space, Each time the observer moves, the difficulty increases because complex calculations must be performed in real time.

[0017] As a prior art aiming to solve this problem, Japanese Patent Laid-Open No. 5-266216 JP 2003-263651 A, S. Both of these are technologies that simplify the rendering process of volume data by introducing a slice-like surface model representation format into the volume data representation format.

FIG. 12 is a diagram schematically showing a concept of introducing a sliced surface model representation format into the volume data representation format.

In the conventional technique shown in FIG. 11, the sampling process and luminance sum of products calculation process performed separately for each ray are executed. In the conventional technique shown in FIG. 12, the volume data is sliced and divided. Each slice plane is described as polygonal data as a surface model. By preparing volume data as a stack of surface models for each slice plane in this way, sampling processing and luminance value processing for each ray can be performed collectively for each slice plane. For example, if the opacity is given to the surface model of each slice surface, the final luminance value of each pixel can be determined as if a plurality of translucent sheets are overlapped. In addition, when the observer moves through the volume, it is possible to perform pseudo-drawing inside the volume by processing 2D drawing of the slice plane according to the viewpoint with polygon data at high speed. .

Patent Document 1: Japanese Patent Laid-Open No. 5-266216

Patent Document 2: Japanese Patent Laid-Open No. 2003-263651

Disclosure of the invention

Problems to be solved by the invention

[0020] As described above, the introduction of the sliced surface model representation format into the volume data representation format can reduce the calculation cost, and the observer may move in the virtual reality space. It is possible to execute the 3D rendering process inside the volume in a pseudo manner.

However, the conventional rendering processing technique has the following problems.

The first problem is the loss of nature. It is preferable to draw the acquired volume data as close as possible to the physical phenomenon of the substance and to represent the state. S In order to introduce a fiss model, a plane-like constraint relationship is created between the botasels, and the naturalness is lost. In other words, smoke is present in a three-dimensional space with a spread V, but since a slice-like surface model is introduced, the button cell is described as triangular polygon data on the slice plane (Japanese Patent Application Laid-Open No. Hei 5). — Fig. 5 of 266216)) The feature of spreading in 3D space cannot be expressed.

[0022] The second problem is a problem of fluctuation expression. Fluctuation data is given to the acquired volume data itself, but smoke is flowing in a three-dimensional space! /, And it flows with fluctuations not only in the vertical and horizontal directions but also in the longitudinal direction In the rendering process, if this fluctuation can be expressed, it can be drawn so as to represent a state closer to the physical phenomenon of the substance. However, if rendering processing is performed using the above-described conventional technology, it is not possible to express the fluctuation of an entity such as smoke, etc. at a small calculation cost! /.

[0023] The third problem is the problem of expressing the flow velocity of particles. The acquired volume data includes the movement of macro volume data. For example, in the case of smoke, it cannot be expressed that smoke particles flow and move! And it will be expressed as such. If the flow velocity of smoke particles can be expressed appropriately, it can be visualized to represent a state closer to the physical phenomenon of the substance, and the viewer can intuitively feel the flow velocity of the drawing object such as smoke. It becomes easy to do.

[0024] In view of the above problems, the present invention can flexibly add fluctuation expression of three-dimensional volume data while suppressing an increase in calculation cost, and can be easily grasped by a viewer. An object of the present invention is to provide a volume data rendering system and a volume data rendering method that can also express the flow velocity of the volume data. Means for solving the problem

[0025] To achieve the above object, a volume data rendering system according to the present invention includes a button cell data set generation module that generates a button cell data set to which a luminance value and opacity are given based on the volume data. A ray casting module that samples a voxel along a ray from the botacell data set, and generates pixel data to be drawn based on a luminance value and opacity of the botacell for the sampling; A drawing module for drawing data, Ray-casting module force The feature is that the coordinate position of the botacell that is useful for the sampling is varied based on a fluctuation model.

[0026] In the above configuration, it is preferable that the fluctuation model is a systematic fluctuation model that reflects fluctuation of a physical phenomenon expressed by the volume data. For example, if the volume data to be drawn is smoke at the time of a fire, a systematic fluctuation model that reflects how the smoke rises while fluctuating with smoke. Generally, a turbulent phenomenon such as smoke is characterized by a statistical quantity, so it is preferable to prepare a fluctuation volume that reflects the frequency characteristics of the spatial density distribution in the phenomenon that actually occurs. Further, in the above configuration, it is preferable that the fluctuation model force also includes a description of fluctuation of the shade data of the button cell. Here, the hue data is data relating to pixel color representation, such as additive color mixing RGB data, subtractive color mixing CMYK data, developer Munsell color system data, and HIS color system data. .

[0027] Further, a fluctuation model database storing a plurality of fluctuation models is provided, and a systematic fluctuation model that reflects fluctuations of a physical phenomenon expressed by the volume data from the fluctuation casting model database is provided. It is also preferable to select and equip it.

[0028] In addition, in the fluctuation of the coordinate position of the botacell applied to the sampling based on the fluctuation model force of the ray casting module, a physical phenomenon represented by the volume data with respect to the magnitude and direction of the fluctuation. It is also preferable to adjust the speed field model that reflects the moving speed.

[0029] Further, a velocity field model database storing a plurality of velocity field models is provided, and the velocity field model reflecting the moving speed of the physical phenomenon expressed by the recasting module force, the velocity field model database force, and the volume data. It is preferable that it can be selected and equipped.

[0030] Further, the fluctuation model force is defined in the form of a fluctuation volume in which a fluctuation function is arranged in each of the botasels, and the velocity field model is defined in the form of a velocity field volume in which a function representing the velocity is arranged in each of the botasels, An index volume that holds reference information indicating which bot cell is referred to in the fluctuation volume; The fluctuation volume and the velocity field volume are linked via a yum, the ray casting module force is updated to reflect the influence of the velocity field volume on the physical phenomenon, and the index volume reference information is updated. It is also preferable to change the coordinate position of the volume data related to the sampling by using a fluctuation function arranged in the fluctuation volume indicated by the reference information.

The invention's effect

[0031] According to the volume data rendering system of the present invention, the ray casting module changes the coordinate position of the botacell, which is useful for sampling, based on the fluctuation model. It is possible to obtain a volume data rendering system capable of flexibly visualizing fluctuation expressions of volume data such as smoke while keeping the naturalness of 3D volume data while suppressing cost increase.

[0032] According to the volume data rendering system of the present invention, the sampled botacell coordinate position can be changed based on the ray casting module force fluctuation model!調整 Since the speed field model that reflects the movement speed of the physical phenomenon expressed by the volume data is added to the magnitude and direction of fluctuation, the smoke flow rate is reduced in the rendering result of the rendered object such as visualized smoke. It can be expressed appropriately, and viewers can easily perceive the flow velocity of the drawing object such as smoke.

BEST MODE FOR CARRYING OUT THE INVENTION

[0033] The volume data rendering system of the present invention, in the obtained volume data rendering process, suppresses an increase in calculation cost and maintains naturalness close to the physical phenomenon of the substance, while maintaining fluctuation expression and particle velocity. Expression is also possible. In the present invention, the concept of fluctuation volume describing the characteristic fluctuations of the physical phenomenon to be drawn is introduced, and in the sampling process of each botacell, fluctuations are made in the sampling process of the botacell while referring to the fluctuation volume. Give.

[0034] A configuration example that enables fluctuation expression as Example 1, a configuration example that enables fluctuation expression and particle velocity expression as Example 2, and a further application extension as Example 3 is possible. An example of a functional configuration is shown.

Example 1

[0035] An example of the configuration of a volume data rendering system that enables fluctuation expression according to the first embodiment will be described.

FIG. 1 is a diagram schematically illustrating a basic flow of a rendering process in the volume data rendering system according to the first embodiment of the present invention.

In the volume data rendering system according to the first embodiment of the present invention, first, volume data acquisition processing (S 1), and luminance value and opacity determination processing (S 2) for each of the botasels are performed. These processes may be the same as the flow of the volume rendering process according to the prior art shown in FIG.

[0037] In the ray casting process of the present invention, a sampling coordinate position determination process (S10) is added to the fluctuation process, and the fluctuation process (S10) is compared to the sampling process (S3) of the botacell. ) Is reflected!

In the prior art botacell sampling process, as shown in FIG. 11, the botacell is sampled at regular intervals along the path of the ray, and the sampled voxel is fixed. In the conventional technology, the distance between the surfaces is fixed, and the result is that the samples are sampled at regular intervals along the path of the ray. It can be said that it is the same as the thing.

Therefore, in the volume data rendering system of the present invention, each sampled botacell has a spatial fluctuation according to the fluctuation model based on the fluctuation model. The brightness value and hue of the image are not constant and fluctuations occur. The final luminance value integration calculation results in fluctuations, and the fluctuations are reflected in the luminance values and hues of the pixels that are the rendered rendering results.

[0039] FIG. 2 is a diagram schematically showing fluctuations in the coordinate position of the sampled botacell in the sampling process of the volume data rendering system of the present invention.

Reference numeral 200 denotes a volume data Botacel data set. Botacell as lattice unit Is formed. 201 schematically represents a sampled bocellel. 300 is Ley.

[0040] The top diagram of FIG. 2 shows a state of sampling processing of a voxel data set by ray casting for drawing the first frame. It can be seen that the fixed ray sampling shown in Fig. 11 has a spatial fluctuation. The coordinate position of the bot cell 201 sampled along the ray path fluctuates three-dimensionally. Based on this sampling result, the pixel value of the corresponding pixel in the first frame is determined.

[0041] The middle diagram of FIG. 2 shows a state of sampling processing of the voxel data set by ray casting for drawing the nth frame. It can be seen that the sampled botasel 201 in the center diagram of FIG. 2 has fluctuations relative to the sampled botasel 201 in the top diagram of FIG. This fluctuation is the fluctuation caused by the passage of the first frame force n frame time at the top of Fig. 2, that is, the temporal fluctuation.

[0042] As described above, the volume data rendering system of the present invention can incorporate spatial fluctuations in one frame, and further can incorporate temporal fluctuations between frames in a visualized image displayed as a moving image. it can. In this way, if the description of the fluctuation model used for fluctuation processing (S 10) has not only spatial fluctuation but also temporal fluctuation, the botacell coordinate position to be sampled fluctuates between frames based on the fluctuation model. In other words, fluctuations are reflected in the luminance value of each botasel and the luminance value calculated by integrating the opacity force, and the rendering result can be given fluctuations.

[0043] Here, in the above fluctuation processing, if a systematic fluctuation model reflecting the fluctuation of the physical phenomenon expressed by the volume data to be drawn is introduced, the entity to be drawn in the rendering result is introduced. It is possible to express the fluctuations reflecting the physical phenomenon. Detailed explanation of this point will be described later.

[0044] As a result of the sampling process in the ray casting process, the luminance value of the sampled voxel is i, the opacity is _α , and the incident luminance value incident on this buttonel is I.

m

Assuming that the emission luminance value when exiting the kessel is I, the emission luminance value of the botacell is

out

In the conventional technology, it is represented by the number 2, which is the same formula as the number 1 described above. The pixel values that are finally drawn are sampled through a fluctuation process along the path of the corresponding ray, and are integrated by the following equation (2) by the botacell.

[0045] [Equation 2]

I ou t = I i n (1 —ct) + i

[0046] Drawing processing of each pixel is executed, and volume data such as smoke is drawn on the monitor.

The integration process (S4) and the pixel rendering process (S5) shown in FIG. 1 may be the same as the flow of the volume rendering process according to the prior art shown in FIG.

This is the basic processing flow of the volume rendering system of the present invention.

Next, a configuration example of the system will be shown.

FIG. 3 is a diagram showing an example in which the volume data rendering system 100 is specifically constructed by processing modules. Each processing module can be composed of a general-purpose CPU and memory system. A dedicated accelerator such as DSP can be used.

Reference numeral 110 denotes a volume data acquisition module. For example, volume data given as simulation data is captured. An external input interface may be provided and external force volume data may be captured via a network.

[0049] Reference numeral 120 denotes a button cell data set generation module. A luminance value determination module 121 and an opacity determination module 122 are provided. Volume data acquisition module 110 Receives volume data from 10 and expands it for each botacell, and obtains a data set of its luminance value and opacity.

A loop is formed between the volume data acquisition module 110 and the button cell data set generation module 120. Volume data often changes as the simulation progresses. Since a new botacell data set reflecting the volume data update must be prepared, new volume data is acquired through the volume data acquisition module 110 at each volume data update cycle, and Need to be generated. Therefore, as shown in the figure, the processing by the volume data acquisition module 110 and the botacell data set generation module 120 forms a loop.

[0051] 130 is a ray casting module. Ray casting module 130 A sampling module 131, an integration module 132, and a fluctuation processing module 133 are provided.

[0052] The sampling module 131 first determines the original sampling coordinates d (x, y, z) according to a predetermined rule. For example, one ray corresponding to a certain pixel as shown in FIG. 11 is selected, and the coordinate value d (x, y, z) of the botacell at a predetermined interval is determined along the path through which the ray passes through the volume. . The sampling module 131 passes the sampling original coordinates d (x, y, z) to the fluctuation processing module 133.

[0053] The fluctuation processing module 133 includes a systematic fluctuation model that reflects fluctuations in physical phenomena expressed by volume data, and for sampling original coordinates d (x, y, z) that are at predetermined intervals, Convert to sampling fluctuation coordinates U (t, d) considering fluctuations. Based on the fluctuation model, the sampling original coordinate d (x, y, z) received from the sampling module 131 is used to generate the sampling fluctuation coordinate U (t, d). The fluctuation processing module 133 is provided with a fluctuation model volume in which fluctuation values are given to each button cell. The fluctuation value is given as a vector with three components x, y and z.

The sampling module 131 receives the sampling fluctuation coordinate U (t, d) from the fluctuation processing module 133, and determines the botacell at the coordinate position as the sampling target. The ray casting module 130 accesses the voxel data set generation module 120 based on the sampling fluctuation coordinates U (t, d), and acquires the luminance value and opacity of the botacell at each coordinate position. Thereafter, the integration module 132 performs integration based on Equation 2. This integration value is the pixel value of the target pixel.

The drawing module 140 receives the luminance value integrated from the ray casting module 130 and draws the pixel on the monitor according to the luminance value. If all the pixels are drawn by the drawing module 140, one frame in which the volume is visualized is completed. When the simulation display of the volume data is a moving image, the frame needs to be rewritten every predetermined frame period. Therefore, the ray casting module 130 and the drawing module 140 form a loop. For example, when displaying at 30 frames per second, the loop processing by the ray casting module 130 and the drawing module 140 is performed. Repeat 30 times per second. In this 30-frame visualized image, fluctuation processing that reflects fluctuations in the physical phenomenon expressed by the volume data at the sampling coordinate position of the botacell is added, and as a result, smoke fluctuates in a form that is close to reality. With V, it becomes possible to give such an effect.

FIG. 4 is a diagram schematically showing the concept of fluctuation processing in the present invention.

In FIG. 4, 200 is a volume data set. 210 schematically shows the fluctuation volume. The fluctuation volume 210 is a kind of mapping vector space in which a fluctuation function is arranged in each botacel in a three-dimensional space based on the fluctuation model. Given a coordinate d (x, y, z), it converts it into a fluctuation function U (t, d) that is placed in the button cell at that coordinate position.

[0057] In the case of the prior art, as indicated by the dotted arrows, the coordinates d (x, Get the brightness value and opacity of the voxel located at y, z).

However, in the volume data rendering system of the present invention, V and coordinate conversion are performed on the fluctuation volume, and the force also accesses the volume data. As indicated by the solid arrow, first, a certain coordinate d (x, y, z) is given to the fluctuation volume, and the fluctuation function U (t , d). Based on the converted fluctuation function U (t, d), the fluctuation function U (tl, d) at the time tl corresponding to the frame to be rendered is specified, the volume data is accessed, and the coordinate position d + Get the brightness value and opacity of the Botacel placed in U (tl, d)!

Next, an example of the fluctuation volume 210 is shown.

The general form of the fluctuation volume is represented by the following map.

U: (x, y, z) eR ³ → R ³

It is also desirable to satisfy the following properties (1) and (2).

(1) Average is 0

(2) Having a characteristic length (The frequency component obtained by Fourier transform has a characteristic peak)

[0059] It should be noted that, as a model of fluctuation processing that is taken into account in the determination processing of the sampling coordinate position, naturalness close to fluctuation of a physical phenomenon expressed by volume data to be drawn is countered. It is preferable to use a systematic fluctuation model to be projected. For example, if the volume to be drawn is smoke, adopting a fluctuation model that models the characteristic fluctuation pattern seen when the smoke rises, the degree of fluctuation of the visualized smoke volume data! When it comes close to the flickering of the smoke of the substance, the effect is obtained.

[0060] The fluctuation volume u (t, d) relating to smoke is generated by the following procedure. First, all fluctuations are initialized to zero. Next, the position r (x, y, z) in the volume is selected at random, and each bot-cell d holds and changes the following Equation 3 in a normal distribution for each fluctuation component.

[0061] [Equation 3] u (t, d) ^ u (t, d) + k exp (-(| dr | ² ) / l)

[0062] Here, 1 is the characteristic size of the pattern formed by smoke. It is possible to give more fluctuations to k and l. By repeatedly adding perturbations to the fluctuation volume according to the above equation, fluctuations with strong short-range autocorrelation are generated.

[0063] Next, the present invention provides the power to introduce fluctuations in the determination of the coordinate positions of the sampled botasels as described above. Further, the present invention directly applies fluctuations to the luminance values and color data of the sampled botasels. It is also possible to introduce. Even if the changes in luminance values and hues between adjacent botasels in the volume data set are small, it is possible for viewers to make adjustments by directly introducing fluctuations in the luminance value and hue data. Therefore, it is possible to ensure an easy-to-understand visual effect on the fluctuation of volume data such as smoke that has been visualized.

[0064] An example of the fluctuation volume that gives fluctuations to the luminance value and hue data of the sampled button cells can be assumed as follows.

For example, in the case of additive color mixture RGB data,

U: (R, G, B) eR ³ → R ³

For example, in the case of HSI data,

U: (H, S, I) eR ³ → R ³

[0065] The rendering system of the present invention not only draws stationary objects such as clouds, but also flows like smoke. It is capable of rendering volume data that changes dynamically, such as physical objects. Therefore, access to volume data via the fluctuation volume shown in Fig. 4 needs to be updated periodically.

[0066] The first update process is an update process performed for each frame period. For example, if display processing of 30 frames per second is performed, sampling processing and integration processing of the voxel at the coordinate position indicated by the fluctuation volume 210 are executed every 1 Z30 seconds, and drawing processing of each pixel of the next frame is executed. . In this way, access is made from the fluctuation volume 210 to the volume data 200 every 1Z30 seconds, and drawing processing is performed while expressing the subtle fluctuations of smoke particles reflecting the fluctuation movement of actual smoke. In consideration of the quality of drawing, for example, frames can be dropped and updated every 1Z15 seconds or updated every 1Z10.

[0067] The second update process is an update process performed at each update cycle of the volume data 200.

When a 3D object to be drawn moves to a macro or is deformed, the volume data 200 itself is updated and updated at an appropriate timing and replaced with the volume data 200. For example, when expressing macro movement or deformation such as smoke moving along a wall surface or being swept away by wind, the volume data 200 itself is updated. For example, update every 0.5 seconds, 1 second later, etc. at an appropriate timing according to the speed of the macro change of the 3D object.

Example 2

[0068] The volume data rendering system according to the second embodiment of the present invention is a configuration example in which the flow velocity of particles can be expressed in addition to the fluctuation of particles in the volume data according to the first embodiment.

In a fire in a tunnel or underground mall, the flow of air in a tunnel or underground mall has a significant effect on the movement of smoke. Here, since the macro movement of smoke on the air flow is originally described in the simulation data, the rendering system should basically draw in accordance with the simulation. However, objects such as smoke are often given in blocks called volume data, which are not described as individual movements of particles in simulation data. For this reason, appropriate rendering is performed on the rendering system side. If you don't understand it, it will be expressed as a relatively lumpy movement. In addition, it was difficult for the viewer to feel the smoke flow rate, and there were many cases.

[0069] Therefore, in Example 2, in addition to the fluctuation expression that reflects the characteristics of the physical phenomenon of smoke introduced in Example 1, a fluctuation expression that reflects the influence of external forces such as wind is introduced. This is a visualization that makes it easier for the viewer to feel the smoke flow rate.

FIG. 5 is a diagram schematically illustrating a basic flow of a rendering process in the volume data rendering system according to the second embodiment of the present invention.

[0070] In the volume data rendering system according to the second embodiment of the present invention, as in the volume data rendering system according to the first embodiment, the fluctuation processing is added to the ray casting process. The fluctuation processing according to the second embodiment (S10a) Is a fluctuation expression that incorporates the expression of the flow velocity of particles, and is a visualization that makes it easy for viewers to realize the flow velocity of particles.

[0071] Other volume data acquisition processing (S1), luminance value and opacity determination processing (S2), sampling processing (S3), integration processing (S4), and rendering processing (S5) for each bota cell are implemented. Same as 1

[0072] The volume data rendering system of the second embodiment introduces the concept of velocity field volume in order to allow expression of particle flow velocity in addition to expression of particle fluctuation in volume data. The velocity field volume is a kind of mapping vector space in which a function representing velocity is arranged in each three-dimensional space based on the velocity field model. Given a certain coordinate d (x, y, z), it converts it to the velocity v (t, d) placed in the button cell at that coordinate position.

[0073] In the volume data rendering system of the second embodiment, the ray casting module performs fluctuation processing in the fluctuation processing module after reflecting the influence of the surrounding environment such as wind via the velocity field processing module. It has become a thing.

The volume data rendering system of the second embodiment needs to perform an operation of functions arranged in these two three-dimensional vector space botasels while maintaining the velocity field volume and the fluctuation volume. Therefore, we introduce an index volume that has a three-dimensional vector space buttonel and holds the reference points.

FIG. 6 is a diagram schematically showing the concept of fluctuation processing reflecting the flow velocity expression of the second embodiment. The

In FIG. 6, the volume data set 200 and the fluctuation volume 210 are the same as those in FIG.

The index volume 220 is a volume that holds the reference point of the fluctuation model volume 210. The index volume 220 has the same three-dimensional space as the volume data 200, the fluctuation volume 210, and the velocity field volume 230. In the index volume 220, it is preferable that consecutive values are stored in each of the button cells at the time of initialization. For example, i (r) = r.

[0076] The velocity field volume 230 includes a model describing the influence of wind and the like, and each three-dimensional vector data is given to each button cell. For example, v (r) is expressed.

Since the fluctuation model volume 210 is referred to via the index volume 220, changes that move from moment to moment due to the influence of the speed field can be reflected and held in the index volume. For example, move the reference point as shown in Equation 4 below.

[0077] [Equation 4] ij Cr) + k _v vCr)

[0078] In the case of the prior art, as indicated by the dotted arrows, the coordinates d (x, y, z) of the volume data are directly set using the coordinates d (x, y, z) as a clue force for the volume data. Get the brightness value and opacity of the voxel located at y, z).

However, in the volume data rendering system of the second embodiment, as indicated by the solid line arrows, the flow velocity expression by the velocity field volume 230 is reflected and the coordinate transformation by the fluctuation model volume 210 is performed, and the force also accesses the volume data.

First, a certain coordinate d (x, y, z) is given to the index volume 220, and the reference coordinate i (t, t) possessed by the boat cell arranged at the coordinate d (x, y, z) in the index volume 220 is given. Convert to d). Next, the reference coordinate i (t, d) is given to the fluctuation volume 210, and the fluctuation function u (t, i (t, d) possessed by the button cell arranged at the reference coordinate i (t, d) in the fluctuation volume 210 is given. )). Based on the converted fluctuation function u (t, i (t, d), the fluctuation function u (tl, i (tl, d)) at the time tl corresponding to the frame to be rendered is specified. Volume day The brightness value and opacity of the button cell located at the coordinate position d + u (tl, i (tl, d >>).

[0080] As described above, since the reference coordinates of the index volume 220 move in a manner that reflects the influence of wind and the like, the brightness value and the opacity change speed also change according to the reference coordinate movement speed. Therefore, rendering that visualizes the flow velocity of particles such as smoke is possible.

FIG. 7 is a diagram showing an example in which the volume data rendering system 100 is specifically constructed by processing modules. Each processing module can be composed of a general-purpose CPU and memory system. A dedicated accelerator such as DSP can be used.

In the second embodiment, in addition to the sampling module 131, the integration module 132, and the fluctuation processing module 133, the velocity field processing module 134 is added to the ray casting module 130! /.

In the case of FIG. 3 of the first embodiment, the sampling module 131 determines the sampling original coordinates d (x, y, z) according to a predetermined rule, and performs the fluctuation processing on the sampling original coordinates d (x, y, z). In the case of Example 2, the sampling module 131 determines the sampling original coordinates d (x, y, z) according to a predetermined rule, and first passes it to the velocity field processing module 134.

[0084] The velocity field processing module 134 has a model that describes the influence of the surrounding environment such as wind, and the velocity field model is applied to the sampling original coordinates d (x, y, z) received from the sampling module 131. Based on the shift process reflecting the flow velocity of smoke, etc., the reference coordinate i (t, d) of the button cell at the corresponding coordinate position of the index volume is generated. In other words, the original sampling coordinates d (x, y, z) are converted into reference coordinates i (t, d) that take into account the movement of smoke particles due to wind.

The fluctuation processing module 133 receives the reference coordinates i (t, d) from the velocity field processing module 134 and captures the fluctuation processing based on the fluctuation model for the reference coordinates i (t, d). Sampling fluctuation coordinates u (t, i (t, d). That is, the fluctuation processing module 133 uses the received reference coordinates i (t, d) for sampling fluctuation coordinates u (t , i (t, d). Sampling module 131 receives sampling fluctuation from fluctuation processing module 133. Coordinates U (t, i (t, d) are received and the button cell at the coordinate position is determined as the sampling target.

As described above, in the second embodiment, the ray casting module 130 performs the fluctuation processing in the fluctuation processing module 133 after reflecting the influence of the surrounding environment such as wind via the velocity field processing module 134. It is going to be done.

The ray casting module 130 accesses the button cell data set generation module 120 based on the sampling fluctuation coordinates u (t, i (t, d), and obtains the brightness value and opacity of the button cell at each coordinate position. The integration module 132 performs integration based on the above-described equation 2. The integration value becomes the pixel value of the target pixel, and the drawing module 140 calculates the luminance value integrated from the ray casting module 130. Then, the pixels are drawn on the monitor according to the luminance value, and if all the pixels are drawn by this drawing module 140, one frame in which the volume is visualized is completed.

As described above, the volume data rendering system according to the second embodiment can incorporate spatial fluctuations in one frame, and further, in a visualized image displayed as a moving image, a flow velocity that reflects the influence of wind or the like. It is possible to incorporate temporal fluctuations between frames incorporating expressions. By performing the fluctuation processing (S 10a) incorporating the flow velocity expression in this way, the sampled botacell coordinate position fluctuates between frames, and it is possible to give fluctuations incorporating the flow velocity expression in the rendering result in a pseudo manner. .

Next, a device for periodic initialization processing of the index volume will be described.

If the velocity field model has different velocities depending on the location (coordinate position) where the influence of the outside world on the volume data such as wind is complicated and not uniform throughout the space, it is located close to the sampling original coordinates. When the two points that were referring to the nearby botacell in the fluctuation volume had different velocities in the velocity field model when the correlation was strong at the beginning, the reference point in the index volume changed over time. Physical phenomena expressed by the volume data to be drawn, because the mutual correlation of the botacell fluctuation coordinates that are separated from each other and referenced in the fluctuation volume is lost, and the mutual fluctuations are simply random. What is the systematic fluctuation that reflects the fluctuations of the world? Volume data rendering system according to Embodiment 2 of the present invention In this case, it is good if the flow velocity of the particles due to the influence of wind etc. can be easily visualized by the viewer, so it is good if the shift amount of the reference coordinates in the index volume can be reflected based on the velocity field model. Initializing coordinates is not a big problem. Therefore, it is possible to devise a method to periodically initialize the index volume and return it to a state in which consecutive values are stored in each botasel. If the index volume is periodically initialized in this way, it is possible to maintain moderate correlation between data that are located close to each other in the original sampling coordinates and have a strong correlation with each other.

Example 3

The volume data rendering system according to the third embodiment of the present invention can flexibly replace the fluctuation model of the fluctuation processing module 133 and the velocity field model of the velocity field processing module 134 shown in the first and second embodiments. This is a configuration example.

The drawing target of the volume data rendering system according to the third embodiment of the present invention is not limited to smoke, but in the following, the drawing target is described as smoke as an example.

In a fire in a tunnel or underground mall, the flow of air in a tunnel or underground mall has a significant effect on the movement of smoke. In addition, the flow of air may change significantly, such as the opening and closing of emergency exits in tunnels, the opening and closing of fire doors, fluctuations in air blowing capacity from the air vents, and movement of objects such as arrival and departure of trains in underground railway stations. is there. If this air flow changes significantly, it will be necessary to change the velocity field model that describes the air flow. In the third embodiment, the fluctuation model of the fluctuation processing module 133 and the speed field model of the speed field processing module 134 can be flexibly exchanged.

[0091] The state of smoke fluctuation may vary depending on the material being ignited, the oxygen concentration in the space, the temperature, the scale of the fire, and the like. Since the conditions that affect the smoke fluctuation condition vary depending on the progress of the fire and the scale of the fire, it is preferable to dynamically adopt a fluctuation model that appropriately represents the smoke fluctuation condition.

FIG. 8 is a diagram showing an example in which the volume data rendering system 100 according to the third embodiment is constructed by the processing module. Each processing module may be composed of a combination of general-purpose CPU and memory system. A dedicated accelerator such as DSP may be used. In the third embodiment, the ray casting module 130 includes a sampling module 1 31, an integration module 132, a fluctuation processing module 133, and a velocity field processing module 1 34, a fluctuation model database 135 and a velocity field model. A database 136 is provided.

[0094] The fluctuation model database 135 stores a plurality of fluctuation models according to the material being ignited, the oxygen concentration in the space, the temperature, the scale of the fire, and the like.

The speed field model database 136 stores a plurality of speed field models corresponding to the opening / closing of emergency exits, the opening / closing of fire doors, and fluctuations in the blowing capacity from the ventilation openings.

[0095] The fluctuation processing module 133 detects information such as the ignited material, the oxygen concentration in the space, the temperature, the scale of the fire, etc. by itself or receives notification from an external force, and fluctuates the fluctuation model accordingly. Equipped from the model database 135 and dynamically equipped.

[0096] The speed field processing module 134 detects information such as the opening / closing of the emergency exit, the opening / closing of the fire door, and the fluctuation of the air sending capacity from the air outlet, or receives the notification from the outside, and the speed field model corresponding to it. Is extracted from the velocity field model database 136 and dynamically equipped.

As described above, the volume data rendering system according to the third embodiment of the present invention can dynamically replace the fluctuation model and the velocity field model according to various condition fluctuations, and renders the natural fluctuation expressed. Processing can continue.

Example 4

The volume data rendering system of the present invention can be constructed using various computers by providing it as a program describing processing steps for realizing the configuration described above. The program including the processing steps for realizing the volume data rendering system of the present invention is not limited to a portable recording medium such as a CD-ROM, DVD, or flexible disk as shown in the configuration example shown in FIG. The program server on the network can be downloaded. When a program is executed, the program is loaded on the computer and executed on the main memory.

[0099] Further, not only a compiled source program but also a so-called network. It is also possible to send the intermediate language format to the client computer and run it on the client computer.

Industrial applicability

[0100] The present invention can be applied to a volume data rendering system and volume data rendering processing method for visualizing volume data defined in a three-dimensional space. Brief Description of Drawings

FIG. 1 is a diagram schematically showing a basic flow of a rendering process in the volume data rendering system according to the first embodiment of the present invention.

FIG. 2 is a diagram schematically showing fluctuations in the coordinate position of a sampled botasel in the sampling process of the volume data rendering system of the present invention.

[Figure 3] Diagram showing an example of a system built with processing modules

FIG. 5 is a diagram schematically showing a basic flow of a rendering process in the volume data rendering system according to the second embodiment of the present invention.

[Fig. 6] A diagram schematically showing the concept of fluctuation processing reflecting the flow velocity expression of Example 2.

[Fig.7] A diagram showing an example of building a system with processing modules.

[FIG. 8] A diagram showing an example of constructing a volume data rendering system according to the third embodiment by a processing module.

FIG. 9 is a diagram schematically showing a state in which a program describing processing steps for realizing the volume data rendering system of the present invention is provided.

[Figure 10] Diagram showing the basic flow of the rendering process when volume data is used

[Fig.11] Diagram explaining the concept of ray casting processing

[Fig. 12] Diagram showing the concept of introducing a sliced surface model representation into the volume data representation

Explanation of symbols

[0102] 100 volume data rendering system

110 Volume data acquisition module 120 Botacel data set generation module

121 Luminance value determination module

122 Opacity determination module

130 Ray casting module

131 Sampling module

132 Integration module

133 Fluctuation processing module

134 Velocity field processing module

135 Fluctuation model database

136 Speed field model database

140 Drawing Module

200 voxel dataset with volume data 201 voxenore

202 Ray

210 Fluctuation volume

220 Index volume

230 Speed field volume

Claims

The scope of the claims

[1] A Botacel data set generation module that generates a Botacel data set given brightness values and opacity based on volume data;

A ray casting module that samples a ray cell along a ray from the vessel cell data set and generates pixel data to be drawn based on a luminance value and opacity of the wave cell for sampling;

A volume data rendering system, comprising: a drawing module that receives the pixel data and draws volume data, wherein the ray casting module force varies the coordinate position of the botacell for the sampling based on a fluctuation model.

[2] The volume data rendering system according to [1], wherein the fluctuation model force is a systematic fluctuation model that reflects fluctuations of a physical phenomenon expressed by the volume data.

[3] The volume data rendering system according to [1] or [2], further comprising a description of the fluctuation of the fluctuation model force tint data of the button cell.

[4] Equipped with a fluctuation model database that stores multiple fluctuation models.

4. The volume data rendering system according to claim 1, further comprising: a systematic fluctuation model that reflects fluctuations of a physical phenomenon expressed by the volume data from the fluctuation model database.

[5] According to the velocity field model reflecting the movement speed of the physical phenomenon expressed by the volume data with respect to the magnitude and direction of the fluctuation in the fluctuation of the coordinate position of the botacell for the sampling based on the fluctuation model. The volume data rendering system according to any one of claims 1 to 3, wherein adjustment is added.

[6] It has a velocity field model database that stores multiple velocity field models,

5. The volume data rendering system according to claim 4, wherein the ray casting module force is selected and equipped with a velocity field model that reflects a moving speed of a physical phenomenon represented by the volume data.

[7] Fluctuation model force This is determined in the form of a fluctuation volume in which a fluctuation function is arranged for each button cell. The velocity field model is defined in the form of a velocity field volume in which each botasel has a function representing velocity,

The fluctuation volume includes an index volume that holds reference information indicating which bocell is referred to.

The fluctuation volume and the velocity field volume are linked through the index volume,

The ray-casting module updates the reference information of the index volume by reflecting the influence of the velocity field volume on the physical phenomenon, and the fluctuations are arranged in the fluctuation volume botasels indicated by the reference information for the update. 7. The volume data rendering system according to claim 5 or 6, wherein a function is used to change a coordinate position of a volume cell for the sampling.

[8] Botacel data set generation processing step for generating a botacell data set given brightness value and opacity based on volume data;

A ray casting processing step of sampling a bota cell along a ray from the bota cell data set, and generating pixel data to be drawn based on a luminance value and opacity of the bota cell applied to the sampling; and

A volume processing step for receiving the pixel data and rendering volume data, and in the ray casting processing step, the coordinate position of the botacell for sampling is varied based on a fluctuation model. Data rendering processing program.

[9] Botacel data set generation procedure for generating a botacell data set given brightness value and opacity based on volume data;

A ray-casting procedure for sampling pixel lines along the ray from the button cell data set and generating pixel data to be drawn based on the luminance value and opacity of the button cell for sampling;

And a drawing procedure for receiving the pixel data and drawing the volume data, wherein the coordinate position of the botacell for sampling is varied based on a fluctuation model according to the ray casting procedure. Render Processing method.